Universal trial for lateral cages

ABSTRACT

A method of trialing an intervertebral disc space, including the steps of creating the disc space, inserting a trial into the disc space, wherein the trial has i) a distal head having an upper surface and a lower surface connected by a pair of side walls, the side walls defining planes, and ii) a proximal rod, so that the head and rod form an obtuse angle and the rod extends through at least one of the planes defined by the side walls of the head.

CONTINUING DATA

This application claims priority from provisional application U.S. Ser.No. 61/466,302, filed Mar. 22, 2011, entitled Universal Trial forLateral Cages, the specification of which is incorporated by referencein its entirety.

This application claims priority from provisional application U.S. Ser.No. 61/358,220, filed Jun. 24, 2010, entitled Instruments and Methodsfor Non-Parallel Disc Space Preparation, and is related tonon-provisional U.S. Ser. No. 13/163,471, filed on even date, entitledInstruments and Methods for Non-Parallel Disc Space Preparation, thespecifications of which are incorporated by reference in theirentireties.

This application claims priority from U.S. Ser. No. 61/379,194, filed onSep. 1, 2010, and entitled “Flexible Vertebral Body Shavers”, and isrelated to non-provisional U.S. Ser. No. 13/163,496, filed on even date,entitled “Flexible Vertebral Body Shavers”, the specifications of whichare incorporated by reference in their entireties.

This application claims priority from provisional application U.S. Ser.No. 61/385,958, filed Sep. 23, 2010, and entitled “Multi-Segment LateralCages adapted to Flex Substantially in the Coronal Plane”, thespecification of which is incorporated by reference in its entirety.

This application claims priority from provisional application U.S. Ser.No. 61/410,177, filed Nov. 4, 2010, and entitled “Multi-Segment LateralCages adapted to Flex Substantially in the Coronal Plane”, thespecification of which is incorporated by reference in its entirety.

This application is related to non-provisional U.S. Ser. No. 13/163,517,filed on even date, entitled “Multi-Segment Lateral Cages adapted toFlex Substantially in the Coronal Plane”, the specification of which isincorporated by reference in its entirety.

This application claims priority from provisional application U.S. Ser.No. 61/397,716, filed Nov. 30, 2010, and entitled “LateralSpondylolisthesis Reduction Cage”, and is related to non-provisionalU.S. Ser. No. 13/163,427, filed on even date, entitled “LateralSpondylolisthesis Reduction Cage”, the specifications of which areincorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

In spine surgery, lateral access approaches are increasingly used todeliver interbody fusion cages to the lumbar spine. These lateralapproaches are gaining in popularity because they minimize posteriorand/or anterior tissue damage, as well as reduce operating room time andassociated blood loss, and infection risk. Conventional lateralapproaches include the following: Direct Lateral (transpsoas entryparallel cranially and caudally with the disc space, or retract thepsoas); Anterior-Lateral (anterior to the psoas parallel to the discspace); and Superior/Inferior Lateral (non-parallel lateral access tothe disc space). See instruments A-C in FIGS. 1-5.

The use of multiple lateral approaches has required the development of atrialing system for each approach, thus increasing the number ofsurgical instruments and overall procedure cost. Specifically-angledtrials limit the surgical approaches to the single specific angle of thetrial.

Currently, no conventional trial system allows for determination of theangle of the implanted trial following its satisfactory placement andimaging.

US Patent Publication No. 2008-0077241 (Nguyen) discloses a method ofpreparing a pair of adjacent vertebral endplates, involving a surgicalinstrument having a pivoting distal removable insert, a proximal handleportion, a body portion, and a linkage member positioned between theinsert and the proximal handle portion, the insert having a firstangular position relative to the body. A leading end of the insert maybe placed in a first position between two adjacent vertebral endplatesand moved to a second position between the adjacent vertebral endplatesby impacting the proximal end portion of the surgical instrument. Theinsert may be pivoted to a second angular position relative to the bodyportion by rotating the handle about the body portion and may lock thesecond angular position of the distal insert. The insert may be moved toa third position between the adjacent vertebral endplates by impactingthe proximal end portion of the surgical instrument.

US Patent Publication No. 2008-0065082 (Chang) discloses instruments andmethods for inserting a rasp into an intervertebral space of a spine andusing the rasp to decorticate the adjacent vertebra. More particularly,one embodiment provides an instrument that actively changes the angle ofthe rasp relative to the instrument. The delivery instrument may use agear portion to articulate the rasp. A second gear on the rasp may matewith a corresponding gear on the instrument. As the instrument gearrotates relative to the instrument, the instrument gear drives the raspgear, thereby rotating the rasp to decorticate the vertebra. Trialinserts and methods are also provided to determine an appropriate sizeof a rasp for decortication.

US Patent Publication No. 2008-0140085 (Gately) discloses a method toinsert a spinal implant into a vertebral space, the method including thesteps of: grasping the implant with a distal end of an implant insertiontool; holding a proximal end of the implant insertion tool and insertingthe implant toward the vertebral space; and manipulating the proximalend to apply a yaw movement to the implant while the implant is attachedto the tool and in the vertebral space.

Adjustable TLIF implant inserters are limited in angulation to the axialplane for posterior approach surgeries. These devices do not measure theamount of angulation instilled in the trial. Therefore, there remains aneed for adjustable trials that allow for flexion of angles of insertionand measurement of the insertion angle for a lateral trial.

SUMMARY OF THE INVENTION

Several devices and methods are disclosed for inserting lateral trialsat trajectories skewed from the intervertebral disc space. Each trialincorporates means to enable controlled angulations into the prepareddisc space. These means include bending or pivoting means. Angulationscan be performed intra-operatively (on a mayo stand) or in-situ (duringor following insertion into the disc). The trial also allows formeasurement of the insertion approach/angle to help ensure the implantis inserted at a consistent angle.

Continuously adjustable trials allow for flexible and adaptable anglesof approach based upon patient anatomy, surgical preference and numbersof levels to be fused.

DESCRIPTION OF THE FIGURES

FIG. 1 discloses the conventional paths of direct lateral andanterior-lateral access to a disc space.

FIGS. 2 and 3 disclose lines of sight for direct lateral access to thedisc space, wherein the trajectory is substantially parallel to the discspace.

FIGS. 4a and 4b disclose lines of sight for indirect lateral access tothe disc space, wherein the trajectory is substantially skewed withrespect to the disc space.

FIG. 5 discloses a trial inserted into the disc space via astraightforward lateral approach.

FIGS. 6a-6c disclose an angled trial inserted into the disc space via ananterior-lateral approach, wherein the trial is angled in the transverseplane.

FIGS. 7a-7b disclose angled trials inserted into the disc space via ansuperior-lateral and inferior-lateral approaches, wherein the trials areangled in the coronal plane.

FIGS. 8a-8b disclose side views of angled trials wherein the distal headpivots about the sheath.

FIG. 8c discloses a cross-sectional view of an angled trial wherein thedistal head pivots about the sheath.

FIG. 8d is a side view of the pivoting portion of the trial of FIG. 8 a.

FIG. 8e discloses a cross-sectional view of the proximal end portion ofthe angled trial of FIG. 8 c.

FIGS. 9a-9d disclose side views of angled trials wherein the distal headpivots about the sheath in the coronal plane, wherein the trials havevarying degrees of angulation.

FIG. 10a discloses a first embodiment of a universal trial having aconical range of angulation.

FIG. 10b discloses a close-up view of the distal end portion of thetrial of FIG. 10 a.

FIG. 10c discloses a cross-sectional view of the trial of FIG. 10 a.

FIG. 11a discloses a side view of a second embodiment of a universaltrial having a conical range of angulation.

FIG. 11b discloses a bottom view of the second embodiment of a universaltrial having a conical range of angulation.

FIG. 11c discloses a cross-sectional view of the trial of FIG. 11 a.

FIGS. 12a-12c disclose perspective views of the second embodiment of auniversal trial having a conical range of angulation.

FIGS. 12d-12f disclose side views of the distal end portion of the trialof FIG. 11a set at varying degrees of angulation.

FIG. 13 discloses a cross-sectional view of the universal joint of FIG.11a , wherein the joint has a tongue-and-groove interface.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of the present invention, the sum of angles α+β thatdescribe the head/rod orientation always totals 180 degrees. Likewise,the sum of the angles γ+β always totals 180 degrees.

For the purposes of the present invention, “substantially laterallyinserting a trial” includes inserting the trial from either the lateralor antero-lateral approach.

Now referring to FIGS. 6-9, there is provided a single-plane adjustmentembodiment of the present invention. This embodiment provides variableangular adjustment of the trial head in a single plane.

In some single-plane embodiments, the trial's angulation can be adjustedwithin a patient's transverse plane. This embodiment is most useful whenthe trial is inserted upon a transverse plane and in an anterior-lateralapproach, as shown in FIGS. 6a-6c . Angulation adjustment in this planecan correct for any deviation of the angle of selected approach from apurely lateral approach to enhance ease of insertion, minimize endplatedamage, and determine the angle of approach for implant insertion.

Therefore, and now referring to FIGS. 6a-6c , in accordance with thepresent invention there is provided a method of trialing anintervertebral disc space, comprising the steps of:

a) inserting a trial 1 into the disc space, the trial having i) a distalhead 3 having an upper surface 5 and a lower surface (not shown), andii) a proximal rod 7,

wherein the head and rod form an obtuse angle β when the head is in thedisc space, and

wherein the rod extends substantially parallel to planes defined by theupper surface and the lower surface of the head when the head is in thedisc space.

Also in accordance with the present invention, there is provided amethod of trialing an intervertebral disc space, comprising the stepsof:

a) creating the disc space,

b) substantially laterally inserting a trial into the disc spacesubstantially within a transverse plane, the trial having i) a distalhead having an upper surface and a lower surface connected by a pair ofside walls, the side walls defining planes, and ii) a proximal rod,

wherein the head and rod form an obtuse angle β in the transverse plane.

In some single-plane embodiments, the trial's angulation can be adjustedalong the patient's coronal plane. This embodiment is most useful whenthe trial is inserted at a coronal angle (preferably a caudal angle) viaa direct lateral approach, as shown in FIGS. 7a-b . Angulationadjustment in this plane can correct for any deviation of the angle ofselected approach from a purely transverse approach.

FIG. 7a discloses the coronal angle-variable trial inserted superiorlyalong a direct lateral approach, while FIG. 7b discloses the coronalangle-variable trial inserted inferiorly along a direct lateralapproach.

Therefore, now referring to FIGS. 7a-7b , and in accordance with thepresent invention, there is provided a method of trialing anintervertebral disc space, comprising the steps of:

a) creating the disc space,

b) inserting a trial 11 into the disc space, the trial having i) adistal head 13 having an upper surface 15 and a lower surface 17connected by a pair of side walls 19, the side walls defining a pair ofplanes, and ii) a proximal rod 21,

wherein the head and rod form an obtuse angle γ when the head is in thedisc space,

wherein the rod extends substantially parallel to the pair of planesdefined by the side walls of the head when the head is in the discspace.

Also in accordance with the present invention, there is provided amethod of trialing an intervertebral disc space, comprising the stepsof:

a) creating the disc space,

b) inserting a trial 11 into the disc space substantially within acoronal plane, the trial having i) a distal head 13 having an uppersurface 15 and a lower surface 17 connected by a pair of side walls 19,the side walls defining a pair of planes, and ii) a proximal rod 21,

wherein the head and rod form an obtuse angle γ in the coronal planewhen the head is in the disc space.

In some preferred embodiments, the adjustment trial that coronallyangulates within the coronal plane comprises an internal pusherconnected to the trial head via a threaded rod contained within a sheathand controlled by a proximal knob. The range of angles α that arepreferred with this trial is between 1 degree and 45 degrees, but morepreferably is from 1 degree to 25 degrees. In some preferredembodiments, the knob and rod can have incremental measurement means toeither intra-operatively or in-situ record the desired degree of trialangulation. This measurement can provide the surgeon with the desireddegree of trial angulation following intradiscal placement of the head.The surgeon thus has the means to insure that the implant is inserted atthe same angle as the trial.

Therefore, now referring to FIGS. 8a-8e , in accordance with the presentinvention there is provided an intervertebral trial for assessing anintervertebral disc space, comprising:

-   -   a) a distal head 31 having an upper surface 33 and a lower        surface 35, the surfaces adapted for contacting opposed        vertebral endplates;    -   b) a sheath 37 having a longitudinal throughbore 39, a distal        end portion 41 pivotally connected to the distal head, and a        proximal end portion 43;    -   c) a rod 45 disposed in the throughbore and having a distal end        portion 47 pivotally connected to the distal head and a threaded        proximal end portion 49,    -   d) a knob 51 abutting the proximal end portion of the sheath and        threadably connected to the threaded proximal end portion of the        rod,        wherein rotation of the knob moves the rod longitudinally to        pivot the distal head about the rod.

Also in accordance with the present invention, there is providedintervertebral trial for assessing an intervertebral disc space,comprising:

-   -   a) a distal head having an upper surface, a lower surface, and a        pair of side surfaces connecting the upper and lower surfaces;        the pair of side surfaces defining a pair of planes;    -   b) a sheath having a longitudinal throughbore and having a        distal end portion pivotally connected to the distal head,    -   c) a rod disposed in the throughbore and having a distal end        portion pivotally connected to the distal head and a proximal        end portion,

wherein longitudinal movement of the rod pivots the rod between the pairof planes defined by the sidewalls of the distal head.

In some embodiments, and now referring to FIGS. 9a-9d , the knobcomprises an outer surface 52 having an indicator 54 that indicates adegree of angulation provided by the trial. In FIGS. 9a-9d , the trialsare shown with 0, 5, 10 and 15 degrees of angulation respectively.

Another preferred embodiment of the present invention providesmulti-plane or polyaxial angle adjustment, which allows a conical rangeof angulations between the head and rod. Several embodiments aredisclosed below that enable such polyaxial angulations.

In one universal joint embodiment, the universal joint comprises a) agenerally spherical ball attached to the trial head, and b) a socketattached to the handle shaft, the socket having a collet that iscompressed upon retraction into a sheath and thereby grips the sphericalball to lock the orientation of the trial. In this embodiment, the rodis pulled backward to induce locking of the universal joint.

Therefore, now referring to FIGS. 10a and 10b , in accordance with thepresent invention there is provided an intervertebral trial 61 forassessing an intervertebral disc space, comprising:

-   -   a) a distal head 63 having an upper surface 65, a lower surface        67, and a proximal end portion 68 comprising a substantially        spherical element 69;    -   b) a sheath 71 having a throughbore 73 having a proximal end        portion 75,    -   c) a rod 77 disposed in the throughbore, the rod having a distal        end portion 79 forming a collet, an intermediate portion 81, and        a proximal end portion 83,        wherein the intermediate portion of the rod mates with the        proximal end portion of the throughbore of the sheath,        wherein the substantially spherical element of the distal head        is rotatably received in the collet to form a universal joint.

Refraction of the rod (or advancement of the sheath) causes the colletto close upon the substantially spherical element, thereby locking aposition of the distal head with respect to the rod.

In some embodiments, this polyaxial trial further comprises radiopaquemarkers 70 provided in the head. These markers assist inradiographically determining the location of the head.

In one universal joint embodiment, and now referring to FIGS. 11a -13,the rod 99 is pushed forward to induce locking of the universal joint.In this embodiment, the universal joint comprises of a) a generallyspherical ball 91 attached to a proximal portion of the trial head andb) a poppet 102 having a concavity matching the convexity of the ball,wherein the poppet is formed at the distal end 101 of the rod. The ballis inserted into the throughbore via an open keyway 107 located in thedistal end portion of the sheath. To lock the joint at a desired angle,the poppet is advanced to mate with the ball (see FIGS. 12d-f ).

Therefore, in accordance with the present invention there is provided anintervertebral trial for assessing an intervertebral disc space,comprising:

-   -   a) a distal head 85 having an upper surface 87, a lower surface        89, and a proximal end portion 90 forming a substantially        spherical element 91;    -   b) a sheath 93 having a throughbore 95 having a threaded        proximal end portion 97,    -   c) a rod 99 disposed in the throughbore, the rod having a distal        end portion 101 forming a poppet 102, a threaded intermediate        portion 103, and a proximal end portion 105,        wherein the threaded intermediate portion of the rod threadably        mates with the threaded proximal end portion of the sheath,        wherein the substantially spherical element of the distal head        is rotatably received in the poppet to form a universal joint.

Rotation of the threaded rod causes it to advance distally and thepoppet to bias against the substantially spherical element, therebylocking a position of the distal head.

In some universal joint embodiments, the sphere and poppet are reversed,so that the proximal end portion of the distal head forms the poppet andthe distal end portion of the rod forms a sphere.

Therefore, in accordance with the present invention there is provided anintervertebral trial for assessing an intervertebral disc space,comprising:

-   -   a) a distal head having an upper surface, a lower surface, and a        proximal end portion forming a joint element; the upper and        lower surfaces adapted to contact opposing vertebral endplates;    -   b) a sheath having a longitudinal throughbore having a proximal        end portion and a distal end portion,    -   c) a rod disposed in the throughbore, the rod having a distal        end portion rotatably mating with the joint element to form an        articulating (e.g., a universal) joint, an intermediate portion,        and a proximal end portion,        wherein the intermediate portion of the rod is received in the        proximal end portion of the throughbore of the sheath,        wherein longitudinal distal movement of the rod causes the        distal end portion of the rod to bias against the joint element,        thereby locking a position of the distal head with respect to        the rod.

In some preferred embodiments of the present invention, there isprovided an intervertebral trial for assessing an intervertebral discspace, comprising:

-   -   a) a distal head having an upper surface, a lower surface, and a        proximal end portion comprising a substantially spherical        element;    -   b) a sheath having a throughbore having a threaded proximal end        portion,    -   c) a rod disposed in the throughbore, the rod having a distal        end portion forming a surface for receiving the substantially        spherical element, a threaded intermediate portion, and a        proximal handle attachment,        wherein the threaded intermediate portion of the rod threadably        mates with the threaded proximal end portion of the sheath,        wherein the substantially spherical element of the distal head        is received in at least the surface of the rod to form a        universal joint,        wherein rotation of the handle attachment causes the rod to        advance and the surface to bias against the substantially        spherical element, thereby locking a position of the distal        head.

Also in accordance with the present invention, there is provided amethod of trialing an intervertebral disc space, comprising the stepsof:

a) inserting a trial into the disc space, the trial having i) a distalhead having an upper surface and a lower surface connected by a pair ofside walls, the side walls defining a first pair of planes, the upperand lower surfaces defining a second pair of planes, and ii) a proximalrod,

wherein the head and rod form an obtuse angle when the head is in thedisc space,

wherein the rod extends through at least one of the first pair of planesdefined by the side walls of the head when the head is in the discspace, and

wherein the rod extends through at least one of the second pair ofplanes defined by the upper and lower surfaces of the head when the headis in the disc space, and

b) inserting an implant into the disc space.

In some universal joint embodiments, either the distal end of the sheathor the sphere (or both) can have a generally smooth surface to allow forunconstrained adjustment. Alternatively, these components can havefeatures that allow for adjustment to specific desired predeterminedangulations. These features can include, but are not limited toundercut, rings, spikes, or teeth. In some incremental adjustmentembodiments, and now referring to FIG. 13, the substantially sphericalelement and the concave lip 111 of the throughbore form a tongue andgroove interface comprising tongue 113 and groove 115.

Therefore, in accordance with the present invention, the throughbore ofthe sheath has a distal end portion forming a concave lip for receivingthe substantially spherical element. Also in accordance with the presentinvention, the substantially spherical element and the concave lip ofthe throughbore form a tongue-and-groove interface.

In some embodiments, a spring can be incorporated into the pusher shaftor the sheath to enhance the ease of angle adjustment.

Both the single-plane and multi-plane designs of the present inventionprovide for modular trial heads. The provision of a plurality of headswith a single adjustment handle allows the more costly adjustment handleto be shared across the plurality of heads and so reduces the overallsystem cost.

In some embodiments, the trial is equipped with an angulation indicatorthat reports the extent of angulation produced between the head and rod.

Therefore, in accordance with the present invention there is provided amethod of trialing an intervertebral disc space, comprising the stepsof:

-   -   a) inserting a trial into the disc space, the trial having i) a        distal head having an upper surface and a lower surface, ii) a        proximal rod, wherein the rod and distal head are pivotally        connected, and wherein the head and rod form an obtuse angle        when the distal head is in the disc space, and iii) an        angulation indicator connected to the rod,    -   b) rotating the rod to adjust the obtuse angle, and    -   c) reading the angulation indicator on the trial.

In preferred embodiments, there is provided an intervertebral trial forassessing an intervertebral disc space, comprising:

-   -   a) a distal head having an upper surface and a lower surface;    -   b) a sheath having a throughbore and having a distal end portion        pivotally connected to the distal head,    -   c) a rod disposed in the throughbore and having a distal end        portion pivotally connected to the distal head and a threaded        proximal end portion,    -   d) a knob threadably connected to the threaded portion of the        rod.        wherein rotation of the knob moves the rod longitudinally to        pivot the distal head, and        wherein the knob comprises an outer surface having an indicator        that indicates a degree of angulation provided by the trial.

Also in accordance with the present invention, there is provided amethod comprising the steps of:

a) laterally inserting a variable-angle trial into an intervertebraldisc space,

b) determining an angle set by the trial in the disc space,

c) providing the angle to an implant-inserter apparatus,

d) inserting the implant into the disc space at the angle.

In general, the trials of the present invention are preferablymanufactured out of standard biomedical instrument materials, includingbiocompatible metals such as titanium alloys, cobalt-chrome andstainless steel.

In general, the trials of the present invention may be used inaccordance with the implants, instruments and procedures disclosed in:

-   -   a) U.S. Ser. No. 61/385,958, entitled “Multi-Segment Lateral        Cages adapted to Flex Substantially in the Coronal Plane”, filed        Sep. 23, 2010;    -   b) U.S. Ser. No. 61/410,177, entitled “Multi-Segment Lateral        Cages adapted to Flex Substantially in the Coronal Plane”, filed        Nov. 4, 2010;    -   c) U.S. Ser. No. 61/358,220, filed on Jun. 24, 2010, and        entitled “Instruments and Methods for Non-Parallel Disc Space        Preparation”, and    -   d) U.S. Ser. No. 61/379,194, filed on Sep. 1, 2010, and entitled        “Flexible Vertebral Body Shavers”,        the specifications of which are incorporated by reference in        their entireties.

We claim:
 1. An intervertebral trial for assessing an intervertebraldisc space between opposing upper and lower vertebral endplates,comprising: a) a distal head having an upper surface, a lower surface, atapered distal end portion connecting the upper and lower surfaces, anda proximal end portion consisting essentially of a neck having alongitudinal axis and a substantially spherical element; wherein theupper surface is adapted to contact the upper vertebral endplate and thelower surface is adapted to contact the lower vertebral endplate; andwherein the longitudinal axis of the neck extends between the upper andlower surfaces; wherein the neck has upper and lower surfaces locatedbetween the upper and lower surfaces of the distal head; b) a sheathhaving a throughbore having a threaded portion, c) a rod disposed in thethroughbore, the rod having a distal end portion forming a poppet, athreaded intermediate portion, and a proximal end portion, wherein thethreaded intermediate portion of the rod threadably mates with thethreaded portion of the sheath, wherein the substantially sphericalelement of the distal head has an outer surface that is rotatablyreceived in the poppet to form a universal joint, which allows a conicalrange of angulations between the head and rod.
 2. The trial of claim 1wherein the throughbore of the sheath has a distal end portion forming aconcave lip for receiving the substantially spherical element.
 3. Thetrial of claim 2 wherein the spherical element and lip form a tongue andgroove construction.
 4. The trial of claim 2 wherein rotation of the rodcauses the rod to advance distally and the poppet to bias against thesubstantially spherical element, thereby locking a position of thedistal head.
 5. The trial of claim 1 wherein the proximal end portion ofthe rod forms a handle attachment.